Cooling is beneficial in countless applications ranging from preservation of perishables to the comfort of humans. It is more difficult to incorporate cooling into small applications, and most practical applications of small scale cooling rely upon application of passive cooling, such as that obtained in microelectronic circuitry through component cooling fins and airflow around the cooling fins. Active cooling is much more efficient at removing heat from a given atmosphere, but well known vapor-compression cycle cooling technology poses serious structural impediments to size reduction that, for the most part, have yet to be overcome.
Many practical applications could benefit from a microcooling approach, i.e. localized cooling as differentiated from macrocooling of a large environment. Examples include clothing cooling systems, packaging for items such as food, blood, organs and medical specimens, and cooling wraps for treatment of injuries. Cooling of electronic circuitry, such as that used in a laptop PC, could increase device operating speed and permit higher component densities. Digital computer package performance is highly dependent on efficient heat dissipation. Automobile, military, manufacturing, and many other applications would also benefit. As examples, chemical warfare protection suits would benefit from improved active cooling, and a suitable active heat transfer device could be used to disguise heat signatures of military equipment, rendering detection of the equipment difficult.
Conventional microcooling devices fail to completely satisfy demands caused by these and other applications. Three common microcooling heat transfer systems are phase change material systems, thermoelectric cooling systems and two part vapor compression systems. Phase change systems use ice, paraffin, or other phase change materials. The materials, or an agent cooled by the materials, is put into thermal contact with the object to be cooled, such as human skin within a clothing garment. These devices are simple, but require inconvenient recharging of the phase change materials, presenting a substantial limitation on their use in most applications. Thermoelectric systems utilize the Peltier effect. Electric current passed through a series of semiconductors causes the semiconductors to get hot on one side and cold on the other. Cooling is through a media or direct thermal contact. The devices have few moving parts, but require a significant amount of power for operation. Conventional vapor compression systems use a portable refrigeration unit having essentially conventional refrigeration equipment and a pump which circulates refrigerant to another part such as a vest or garment. These are highly efficient, but awkward and heavy, relegating their use to a very limited number of applications.
Thus, there is a need for an improved device which addresses some or all of the aforementioned drawbacks. There is a further need for a substantially smaller self- contained vapor compression cycle cooling device. A favorable device could be interconnected with other similar devices to form arrays and could be incorporated in many useful devices.